Systems and methods for obscuring data from a data source

ABSTRACT

Systems and methods for obscuring data from a data source include devices and processes that may objectively measure the information loss for the data source that is caused by applying a privacy policy, and may apply a policy to the data source based on the measured information loss. The systems and methods may measure the information loss for a large data source by taking a representative sample from the data source and applying the policy to the sample in order to quantify the information loss. The quantified information loss can be iteratively used to change the policy in order to meet utility and/or privacy goals, and the system can subsequently apply the changed policy to the data source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/843,487 filed on 8 Apr. 2020, (now granted as U.S. Pat. No.11,443,065), which claims the benefit and filing date of U.S.Provisional Application No. 62/831,129 filed on 8 Apr. 2019, both ofwhich are hereby incorporated by reference in their entirety.

BACKGROUND

The ubiquity of data has made it possible to develop empiricalmathematical models and beneficial analytics to, for example, predict alarge number of event types. Events types such as shopping behavior,entertainment preferences, medical conditions, driving actions,financial risk, etc. can now be accurately predicted and/or beneficiallyanalyzed using the expansive amount of data people generate andorganizations record every day.

This, however, comes at a price to personal privacy, as data thatidentifies an individual or that describes something about an individualthat should be kept private, (which may be referred to as personal dataor sensitive data), is contained in the datasets collected byorganizations, and may be disseminated to other organizations orindividuals.

In response to data privacy concerns, personal or sensitive data can besimply removed or redacted or held back from the data stores or datasources of organizations. But depending on the data, this may render thedataset less suitable, or even unusable, for various purposes that arevaluable to the organization and/or to society. In other words, removingor redacting data significantly reduces its analytic value and canreduce the analytic value of the entire dataset.

Thus, it is desirable to provide systems and methods that enable anorganization to balance safeguards to personal privacy with the need toprovide access to the data in its data stores in a manner that reducesthe reduction in analytic value, keeping the data suitable and usablefor various purposes.

BRIEF SUMMARY

Embodiments consistent with the present invention include systems andprocesses that measure information loss on a dataset when the dataset isprotected by a privacy policy. The described embodiments include systemsand processes that efficiently sample a large dataset, apply policies tothe sample, and objectively quantify the data-loss or utility impact ofthose policies, which quantification may be used to select and applyspecific policies to the dataset.

Various embodiments include a system that can include acomputer-readable data storage device containing program instructionsand an associated processor that executes the instruction to perform aprocess or set of operations. The operations can include sampling a datasource to obtain a sample of data that is statistically representative;determining ridge statistics for the sample of data; measuring orotherwise determining a first entropy, or an information baseline, ofthe sample of data; applying the data privacy policy to the sample ofdata; measuring or otherwise determining a second entropy, or aninformation content, of the sample of data with the policy applied;calculating an information loss value based on the difference betweenthe first entropy and the second entropy; and displaying the informationloss value. In some variants, the operations can also include applyingthe data privacy policy to the data source if the information loss valueis within predetermined limits.

Other embodiments can include a process or operations for sampling adata source to obtain a sample of data that is statisticallyrepresentative; determining ridge statistics for the sample of data;receiving a data privacy policy for a dataset of the data source;determining an estimate of information loss caused by the data privacypolicy using the ridge statistics; displaying the estimate of theinformation loss; and, optionally, applying the data privacy policy tothe data source if the estimate of the information loss is withinpredetermined limits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an example of an environment 100for implementing systems and methods in accordance with aspects of thepresent disclosure.

FIG. 2 shows a system block diagram illustrating an example of acomputing system, in accordance with aspects of the present disclosure.

FIG. 3 is a block diagram showing an example of the relationshipsbetween data sources, fingerprints, and ridges, in accordance withaspects of the present disclosure.

FIG. 4A is a flowchart of an example of a process for determininginformation loss and applying a policy to a data source, in accordancewith aspects of the present disclosure.

FIG. 4B is a flowchart of an example of a process for generating afingerprint, in accordance with aspects of the present disclosure.

FIG. 4C is a flowchart of an example of a process for measuring theinformation loss caused by a policy, in accordance with aspects of thepresent disclosure.

FIG. 5 shows an example of descriptive statistics and other data for abasic numeric ridge, in accordance with aspects of the presentdisclosure.

FIG. 6 is a representation of an example of descriptive statistics andother data for a cardinality ridge, in accordance with aspects of thepresent disclosure.

FIG. 7 shows an example of descriptive statistics and other data for asensitivity ridge, in accordance with aspects of the present disclosure.

FIG. 8A shows the first part of an example of descriptive statistics andother data for a string ridge, in accordance with aspects of the presentdisclosure.

FIG. 8B shows the second part of an example of descriptive statisticsand other data for a string ridge, in accordance with aspects of thepresent disclosure.

FIG. 9 is block diagram showing an example of obscuration techniques, inaccordance with aspects of the present disclosure.

FIG. 10A shows a screen shot of an example of an information lossreport, in accordance with aspects of the present disclosure.

FIG. 10B shows a screen shot of another example of an information lossreport, in accordance with aspects of the present disclosure.

FIG. 10C shows a screen shot of another example of quantifiedinformation-loss information, in accordance with aspects of the presentdisclosure.

DETAILED DESCRIPTION

One way to protect privacy in a dataset or data store is to apply onemore privacy policy. A privacy policy is a set of rules, techniques,and/or operations which perturb, redact, or otherwise obscure datawithin or from a dataset, often focused on sensitive data or personaldata. Privacy policies can produce the effect of reducing the precisionof data (e.g. representing date-of-birth as year-of-birth orgeneralizing zip code to state), removing sensitive data elements (e.g.removing social security numbers), or randomizing certain data elements,such as measurements, among other things. In various implementationsdescribed herein, a privacy policy may have numerous associatedparameters, such as parameters that: specify the user(s) that can accessthe data from a data store, specify what portions of data can beaccessed by a specified user, specify the purpose(s) for which the datacan be used, and specify the amount of precision with which to show thedata, among other things. Each policy, depending on its content, type,and parameter set, provides a variable amount of privacy at the tradeoffcost of loss of some analytic value, which may also be referred to asutility.

The privacy-utility tradeoff is a central concern for the multitude ofuseful and beneficial analytics applications which operate withsensitive data. Favoring the privacy extreme, a dataset provided to ananalytics application can simply be represented as randomized entries.This assures that no private information is leaked, but would have noutility for gaining insights. On the other extreme, all collected datacan be utilized as is without privacy protections. The data would havemaximal utility but present a significant risk of being misused, eithermaliciously or accidentally.

How to efficiently and objectively applying one or more a privacy policyto obscure sensitive data while balancing the privacy-utility tradeoffis a technical problem that is central to establishing and sustaining auseful and beneficial analytics practice. But current conventionalsystems for choosing and applying privacy policies do not address thisproblem. Current conventional systems simply apply whatever privacypolicy is selected by a user without regard to the utility cost of thepolicy and without regard to the amount of information loss caused bythe policy. In those conventional systems, policies are appliedsubjectively, at the whim of the current administrator or user.

Unlike convention systems where a privacy policy is subjectively chosenusing human intuition and/or a user's prior experience with otherdatabases, various embodiments of the systems and methods describedherein instead perform an unconventional, unique combination of stepsfor measuring and/or calculating an information-loss factor or estimatethat is unique for a specific privacy policy as it applies to a specificdataset (e.g., database or portion thereof). The same policy will oftenhave different impacts on information loss for different datasets, andvarious embodiments described herein quantify the impact for eachdifferent dataset, which enables objective decisions regarding whetheror not to apply a policy to a given dataset. Similarly, differentpolicies will typically cause different amounts of information loss(e.g., utility) for a single dataset, and various embodiments describedherein quantify those different amounts of information loss to enableobjective decisions regarding selecting a policy to apply to thedataset. By evaluating and quantifying the information loss associatedwith a specific privacy policy and a specific dataset, and applying apolicy to obscure data based on the quantified information loss, variousembodiments described herein remove what were previously subjectivehuman decisions made based on criteria other than information loss(e.g., based on intuition or past experiences with different datasets)and replaces them with rules-based, objective, computerized operationsand decisions.

Measuring the information-loss impact of a privacy policy on data isnon-trivial and doing it efficiently is a difficult technical andpractical problem. A system could, for example, measure theinformation-theoretic content of a data source both before and after apolicy is applied to the data source, using a metric such as Shannon'sEntropy to calculate the amount of information before and after. Thisapproach is not practical or efficient in many real-life systems,however, because it requires repeatedly querying or accessing the datasource to obtain before and after Shannon's Entropy measurements eachtime a policy and/or the policy parameters are changed. This is veryslow and time consuming and it uses large amounts of computingresources. Under this approach, the performance become untenable andimpractical when data volumes become large, and/or when policies arebeing altered frequently. And, altering policies often occurs frequentlyduring the initial phases of an analytic project.

Various embodiments of the systems and methods described herein quicklyand efficiently measure the impact of a privacy policy on a dataset,including a large dataset, in part by accessing the dataset once orinfrequently to build a model, or fingerprint, of the dataset, andthereafter the model is used to calculate the information loss orprivacy impact or utility change caused by different policies. Thefingerprint represents the dataset, and is used instead of the datasetto evaluate the information loss, etc. associated with a new policy.Various embodiments of the systems and methods described herein providea practical solution for measuring how privacy policies impact utilityand for applying one or more policy based on that impact, providing anovel and efficient solution for testing and balancing theprivacy-utility tradeoff.

More particularly, various embodiments described herein providepractical systems and methods for obscuring data from a data sourcebased on the amount of information loss caused by an obscuration policy.Various embodiments may include devices and operations for specifying apolicy, measuring or calculating the information loss caused by thepolicy on a given dataset, associating the specified policy with thedataset, and then applying the specified policy to the data source suchthat only obscured data is available to users. Thus, in one aspect, theembodiments described herein improve the functioning of databases byenabling the objective and automated application of a privacy policy tothe databases, especially large databases. This may be achieved bypartially or completely obscuring a specific portion(s) (e.g., column)of a dataset according to a privacy policy(ies) that is selected or usedaccording to the amount of information loss the policy causes for thatdataset, where the system objectively calculates the amount ofinformation loss.

In another aspect, the embodiments described herein improve thefunctioning of conventional data obscuring technology on the data in adataset (e.g., a database) by providing an automatically and objectivelycalculated information-loss estimate for use in comparing privacypolicies to each other, e.g., according to the amount of informationloss for each policy.

FIG. 1 illustrates a block diagram of an example of a system or anenvironment 100 for implementing systems and methods in accordance withaspects of the present disclosure. The environment 100 may include aquery user 105, a client device 110, an admin user 135, an admin device140, and a computing system 115, which includes a policy engine 130, avirtualized database 123, and one or more data source(s) 125, which maybe referred to in the singular herein for ease of explanation althoughit may comprise two or more data sources.

In one usage example, the query user 105 may use the client device 110to send a query 117 (e.g., a request for data from a data store) to thecomputing system 115, which provides a result 119, after applying aprivacy policy to the requested data (e.g., which may be done by thepolicy engine 130). The privacy policy typically impacts the result 119of any query issued by the user 105, for example, by obscuring some orall of the data in the result 119.

In a similar usage example, the admin user 135 may use the admin device140 to send a policy 217 and associated metadata (e.g., a privacy policyand its parameters 219 and/or commands for application to the datasource 125) to the computing system 115, which provides a response 139,(which may include an information loss report), after calculating theeffect of the policy 217 on the particular data of the data source 125.In various implementations, the response 139 objectively quantifies theinformation-loss impact caused by the policy 217 with respect to thedata from the data source 125, allowing the admin user 135 and/or admindevice 140 to compare and select from among multiple possible policies217 based on their information-loss effects.

In various implementations, the policy 217 may specify to the system 100which obscuring technique or algorithm to apply to a specific portion ofthe data (e.g., a column) from the data source 125, among other things.In various embodiments, the admin user 135 may create, select, and/orcustomize the policy 217 to specify the obscuring technique for thesystem to use, among other criteria. Two examples of obscuringtechniques include obfuscation by hashing a column of data (e.g.,hashing state name data and putting the hash value into the column whenaccessed by the client device 110) and suppression by replacing a columnof data with null values (e.g., removing the state name data and leavingthe column blank when accessed by the client device 110). Variousobscuring techniques and algorithms are discussed in detail below,including with respect to FIG. 9 .

In various embodiments, the client device 110 can be an input/outputdevice or computing device that is communicatively connected (directlyor indirectly) to the computing system 115 via one or more communicationchannels 120. In some implementations, the client device 110 can be aterminal of the computing system 115 or a personal computing device orthe like that provides a user interface. For example, the client device110 may provide the query user 105 with a graphic user interface viawhich the query user 105 can send the query 117 to the computing system115, and receive results 119. The communication channel 120 can comprisea wired or wireless data link and/or communication networks, such as adata bus, a local area network, a wide area network, or the Internet.

As noted previously as a usage example, the query user 105 may use theclient device 110 to send a query 117 (e.g., a request for data from adata store) to the computing system 115. In various embodiments, thepolicy engine 130 can process the query 117 to determine whether any ofthe policies 217 (see FIG. 2 ) and their associated parameters 219 areapplicable to the particular query user 105, data source 125, and/orvirtualized database 123 specified by the query 117, and if so, thepolicy engine 130 can apply the appropriate privacy policy 217 to theresponsive data before providing the result 119 to the client device110. Thus, the query user 105 can only access or see the requested dataafter the data has been obscured according to the privacy policy 217,which may be applicable to some of the users of the client device 110,but not to others, which can be specified, for example, in theparameters 219 associated with a policy 217.

In various embodiments, the admin device 140 can be an input/outputdevice or computing device that is communicatively connected (directlyor indirectly) to the computing system 115 via one or more communicationchannels 150. In some implementations, the admin device 140 can be aterminal of the computing system 115 or a personal computing device orthe like that provides a user interface. For example, the admin device140 may provide the admin user 135 with a graphic user interface viawhich the admin user 135 can send a policy 217 to the computing system115, and receive a response 139. The communication channel 150 cancomprise a wired or wireless data link and/or communication networks,such as a data bus, a local area network, a wide area network, or theInternet.

In various embodiments, the computing system 115 includes hardware andsoftware that perform the processes, services, operations, and functionsdescribed herein. In some embodiments, the computing system 115 can beimplemented as a server. As shown in the example of FIG. 1 , thecomputing system 115 can include or implement a virtualized database123, which interacts with and accesses information from the datasource(s) 125, and a policy engine 130, which interacts with thevirtualized database 123, and also interacts with and accessesinformation from the data source(s) 125. In the embodiment shown, thevirtualized database 123 also interacts with the client device 110 ofthe query user 105, and policy engine 130 also interacts with the admindevice 140 of the admin user 135.

In various embodiments, the data source(s) 125 can be any type ofinformation repository that is queryable. In some implementations, thedata source 125 can be one or more queryable database, which may becolumnated or columnar. In some implementations, the data source 125 canbe or include data structures, such as PYTHON'S PANDAS DATAFRAME™ or RDATAFRAMES™, and/or can be or include data structures for commonconsumer applications, such as MICROSOFT EXCEL™ worksheets or MICROSOFTACCESS™ databases, as are known to those of skill in the art.

In various implementations, the data source 125 can contain PersonallyIdentifiable Information (PII) or other sensitive data. In one use caseexample, the data source 125 can be a collection of information (e.g., adataset) maintained by a healthcare provider, and can contain medical,personal, and other sensitive information regarding patients, caregiversand insurers. In other use cases, the data source 125 can contain humanresources data, business data, financial data (e.g., trade ortransactional data), insurance data, etc.

In various typical implementations, the data source 125 is comprised ofa collection of records (e.g., rows), and each record is comprised of aseries of attributes (e.g., columns), as is commonly known in the art.

While the data source 125 is illustrated as being part of the computingsystem 115 in the example shown in FIG. 1 , it is understood that someor all of the data source 125 could be located or stored remotely fromthe computing system 115 and/or maintained by one or more entitiesdifferent from the entity that provides, operates, or maintains thecomputing system 115.

In various embodiments, the virtualized database 123 can be a databasemanagement system or service that acts as a container to transparentlyview and query other data sources (such as multiple databases or datasources 125) through a uniform interface that presents information frommultiple sources as if they were a single source. For example, multipledatabases (e.g. multiple data sources 125) can look like a singledatabase to the query user 105. The virtualized database 123 can besystem, service, and/or data structure that allows the query user 105 totransparently view and query multiple data sources 125 as if they were aone set of data. By doing so, the query user 105 can access informationof the data source(s) 125 as a single database, without copying,duplicating, or combining the information of the data source(s) 125. Thevirtualized database 123 can be implemented as a queryable databasesystem or service, such as POSTGRESQL, AMAZON REDSHIFT™, APACHE HIVE™,or SQL SERVER™, as are known to those of skill in the art.

In various embodiments, the policy engine 130 can be or include softwareinstructions, a software program, a software application, or dedicatedhardware, such as an application-specific integrated circuit (ASIC) or afield-programmable gate array (FPGA), among other things. In variousembodiments, the policy engine 130 can implement some, a portion of, orall of the processes, functions, and/or operations described herein,including those related to measuring, calculating, and/or reporting theinformation loss caused by applying a policy 217 to a data source 125and to selecting and/or applying a specified policy to the data source125.

Various embodiments of the system 100 may enable an admin user 135 toobjectively balance utility and privacy and understand that these aretwo complimentary things, and can also automatically provide anobjective indication of the highest available utility for a group ofpossible privacy policies or the highest available privacy level for atarget utility. Various embodiments of the system 100 can provide anautomated calculation of the information loss, which represents atradeoff, and instigate the selection and application of an appropriatepolicy(ies).

Other embodiments may similarly provide a system for measuring privacybuilt upon this framework. Such embodiments can enable a holisticalunderstanding of the privacy-utility trade off associated with variouspolicies and obscuring techniques, and objective selections of policiesand techniques that preserve and provide the needed information from adataset while maintaining a minimum threshold of privacy.

One of ordinary skill will recognize that the components, arrangement,and implementation details of the system 100 are examples presented forconciseness and clarity of explanation. Other components, implementationdetails, and variations may be used, including adding, combining, orsubtracting components. For example, there may be two or more datasources 125, some or all of which are external to the computing system115. For another example, the admin device 110 may be removed and itsfunctionality implemented by the computing system 115, which may providea user interface for the admin user 135 via an I/O device 233 asdescribed in FIG. 2 . For yet another example, the client device 110 andthe admin device 140 may be combined into a single device with multiple,different functions for different users 105, 135.

FIG. 2 shows a system block diagram illustrating an example of thecomputing system 115, in accordance with aspects of the presentdisclosure. As shown in this example, the computing system 115 caninclude a computing subsystem 230, an input/output (I/O) device 233, anda storage system 235. The I/O device 233 can be or include any devicethat enables an individual (e.g., an operator, a user, and/or consumer)to interact with the computing subsystem 230 and/or any device thatenables the computing subsystem 230 to communicate with one or moreother computing devices (e.g., client device 110, admin device 140)using any type of communications link (e.g., communication links 120,150). The I/O device 233 can include, for example, a touchscreendisplay, pointer device, keyboard, etc. In various implementations, theI/O device can provide a network interface for the computing system 115to connect with another computing device (e.g., client device 110, admindevice 140, a data source 125).

The storage system 235 can be or include a computer-readable,non-volatile, hardware data storage device that stores informationand/or program instructions. For example, the storage system 235 can beone or more solid state memories and/or hard disk drives. In accordancewith aspects of the present disclosure, the storage system 235 can storeor include the policy engine 130, the policy 217, policy parameters 219,a fingerprint cache 221, and the virtualized database 123, which can bethe same or similar to that previously described. One of ordinary skillwill recognize that the storage system 235 can store multiple instancesof these items, such as multiple policies 217 and their associatedpolicy parameters 219. One of ordinary skill will further recognize thatdepicting the policy 217 and the policy parameters 219 as part of thepolicy engine 130 is a design choice, and other implementations mayorganize the policy 217 and the policy parameters 219 separate from thepolicy engine 130.

In various embodiments, the computing subsystem 230 can include one ormore processors 239 (e.g., a microprocessor, a microchip, or anapplication-specific integrated circuit), one or more memory devices 241(e.g., random access memory (RAM) and read only memory (ROM)), one ormore I/O interfaces 243, and one or more network interfaces 245. Thememory device 241 can be a local, high-speed memory (e.g., RAM and acache memory) employed during execution of program instructions by theprocessor 239. Additionally, the computing subsystem 230 includes atleast one communication channel 247 (e.g., a data bus) by which itcommunicates internally and with the I/O device 233 and the storagesystem 235. In the example shown, the processor 239 executes computerprogram instructions (e.g., an operating system and/or applicationprograms, e.g., an implementation of the policy engine 130), which canbe stored in the memory device 241 and/or the storage system 235. Forexample, the processor 239 can execute the computer program instructionsof the policy engine 130, which functions to, among other thingsdescribed herein, process queries (e.g., query 117) and respond byproducing differentially private (e.g., obscured according to a privacypolicy 217) query results (e.g., result 119).

It is noted that the computing subsystem 230 is only representative ofvarious possible equivalent computing devices that can perform theprocesses, functions, and operations described herein. To this extent,in embodiments, the functionality provided by the computing subsystem230 can be provided by any combination of general purpose hardware,and/or specific purpose hardware (e.g., ASIC, FPGA), and/or computerprogram instructions. In each embodiment, the program instructions andhardware can be created using standard programming and engineeringtechniques, respectively.

The fingerprint cache 221 stores at least one fingerprint, which is aseries of measurements and artifacts about the data source 125. Afingerprint represents the data in a data source 125 in various ways. Invarious implementations, the fingerprint cache 221 may store multiplefingerprints: there may be one fingerprint for each of several differentdata sources 125, and/or there may be two or more fingerprints for asingle data source 125.

In various implementations, a fingerprint is a collection of data thatis derived and/or measured from a data source 125, and which describesor represents the data source 125. The fingerprint can be used to assessthe impact of a privacy policy 217 and its associated parameters 219 onthe information and/or utility of the data source 125. The measurementsincluded in a fingerprint can comprise, but are not limited to,distributional statistics such as counts, averages, variances,distributional moments, common factors, frequencies of occurrence ofthese factors, typical string structures, etc., where thesemeasurements, statistics, and calculations may have been made by thepolicy engine 130 on the data in the data source 125. The artifactsincluded in a fingerprint can comprise, but are not limited to, datastructures such as bloom filters, raw observations, probabilisticsketches, etc. As used herein, each element (e.g., each measurement orartifact) of the fingerprint may be referred to as a “ridge”.

One of ordinary skill will recognize that the components, arrangement,and implementation details of the computing system 115 are examplespresented for conciseness and clarity of explanation. Other components,implementation details, and variations may be used, including adding,combining, or subtracting components and functions.

FIG. 3 shows an example of the relationships between a data source 125,a fingerprint 310, and a set of ridges 315-335. As shown in thisexample, the basic numeric ridge 315, the cardinality ridge 320, the PG(Postgres) stats ridge 325, the string ridge 330, and the sensitivityridge 335 make up the fingerprint 310 that describes and represents thedata source 125. In various implementations, the ridges may includenumeric statistics, descriptive statistics, timestamp statistics, listsof the most frequently occurring values, other frequency metrics, etc.that are used in measuring, estimating, or calculating the informationloss caused by a policy 217, e.g., when applied to a specified dataset(e.g., to a column) of the data source 125.

For example, the basic numeric ridge 315 can include (e.g. store) aseries of descriptive calculation results, artifacts, statistics, etc.about any numeric data within the data source 125, such as the numericdata that is within a column of data from a data source 125. Forexample, the system 115 executing the policy engine 130 may measureand/or calculate several descriptive statistics from a column of data(e.g., a dataset from the data source 125) that contains numbers. Invarious implementations, the statistics may include, e.g., the mean, themedian, the mode, etc. of the column, which can be stored as part of thebasic numeric ridge 315. Similarly, the system 115 and policy engine 130may calculate or create a histogram for the column's dataset, which canbe stored as part of the basic numeric ridge 315.

The measures, metrics, and statics stored in the basic numeric ridge 315are used by the system 115 for calculating the information loss causedby a given privacy policy 217 when applied to the numeric dataset. Forexample, consider the example where the dataset (e.g., a column of datain a spreadsheet) contains numeric annual income data. If the policy 217for the income dataset calls for generalizing (e.g., rounding off) thedata to the nearest $10,000, then there is a significant amount ofinformation loss, particularly compared to, for example, rounding offthe annual income data to the nearest $100. Moreover, the amount ofinformation lost depends on the characteristics of the raw, un-obscureddata that is in the dataset. For example, if the raw data all falls inthe range of $0-$15,000 and the policy 217 for the income dataset callsfor generalizing the data to the nearest $10,000, then almost all of theinformation in the dataset will be lost after applying the roundingpolicy; whereas if the raw data all falls in the range of$150,000-$500,000 and the policy 217 for the income dataset calls forgeneralizing the data to the nearest $10,000, then very little of theinformation in the dataset will be lost after applying the policy.

For another example, the cardinality ridge 320 can include (e.g. store)a series of descriptive calculation results, artifacts, statistics, etc.about any set-type data within the data source 125, for example, stringdata that is within a column of data from a data source 125. Forinstance, the system 115 executing the policy engine 130 may measureand/or calculate several descriptive statistics from a column of data(e.g., from the data source 125) that contains a finite set of characteror numeric values, such as a set of character strings that were chosenfrom a finite list of strings, or a set of ZIP code numbers.

The measures, metrics, and statics stored in the cardinality ridge 320are used by the system 115 for calculating the information loss causedby a given privacy policy 217 when applied the data from which thecardinality ridge 320 was generated. For example, consider the examplewhere the dataset (e.g., a column of data in a spreadsheet) containsU.S. state names, which could be any string from a set of fiftydifferent state-name strings, where the cardinality ridge 320 mayinclude, among other things, a representation (e.g., a percentage) ofthe number of times each of the fifty names occurs in the dataset.

The PG stats ridge 325 can include (e.g. store) a series of descriptivecalculation results, artifacts, statistics, etc. about internalprocesses used by a Postgres implementation to service a query, which isnot useful within an information loss context, but is included forcompleteness.

The string ridge 330 can include (e.g. store) a series of descriptivecalculation results, artifacts, statistics, etc. about a dataset (e.g.,column) that consists of character strings. An example of such a datasetis the above-mentioned dataset that contains U.S. state names, whichcould be any string from a set of fifty different state-name strings.

The sensitivity ridge 335 can include (e.g. store) a series ofdescriptive calculation results, artifacts, statistics, etc. about adataset (e.g., column) that contains information which is automaticallyclassified by the system as sensitive information, for example, socialsecurity numbers, credit card numbers, birth dates, and the like. Invarious embodiments, the system 115 can use a predefined dictionary ofcommon patterns for sensitive information (e.g., numeric data in formatxxx-xx-xxxx, which is a format commonly used for social securitynumbers) to identify datasets or columns that contain sensitiveinformation within a data source 125.

Several of the ridges will be described in greater detail below withrespect to FIGS. 5-8 .

It should be noted that although FIG. 3 shows only one each of ridges315-335 for the sake of clarity and ease of explanation, in variousimplementations, a fingerprint 310 may include multiple instances ofeach of the ridges 315-335, according to how may columns ofcorresponding data are contained in the data source 125. For example, ifthe data source 125 contains 10 columns of numeric data, then thefingerprint 310 may have 10 different instances of the basic numericridge 315, one for each numeric-data column/dataset.

FIGS. 4A-C show examples of processes for generating a fingerprint andmeasuring the impact (e.g., information loss) of policies upon theunderlying data.

FIG. 4A is block diagram of an example of a method or process 400 forobjectively determining information loss and applying a privacy policyto a fingerprint, according to an implementation of the invention. Insome embodiments, all or part of the process 400 may be implemented bythe computing system 115, for example by executing the policy engine130.

In the example shown, at block 405, the computing system 115 receives aprivacy policy 217 and its associated parameters 219, e.g., from theadmin device 140 associated with the admin user 135.

In some use cases, the admin user 135, or an application running on theadmin device 140, may submit or select a policy 217 for the purpose ofdetermining how much information loss would be caused by applying thepolicy 217 to a specific data source 125. The policy 217 may then beeither applied to the data source 125 at the end of the process 400, ornot, based on the amount of information loss calculated by the system115. If not, then the admin user 135/admin device 140 may send or selectanother, different policy 217, to repeat the process 400 in order tofind out its associated information loss and apply it to the data source125 if the information loss versus utility balance is satisfactory,e.g., above a predetermined threshold.

In various implementations, the policy 217 may include or specify one ormore different types and/or instances of data obscuration, which areapplied on a column by column basis to specified columns of the datasource 125. In such implementations, the admin user 135 and/or admindevice 140 may define or specify in the policy what is obscured percolumn, which affects what can be seen or accessed by the query user 105or an application executing on a client device 110.

In some embodiments, the admin user 135 can select a policy 217 from apredetermined group of policies or may otherwise define the policy 217to provide to the system at block 405.

The system 115 can record the time of policy receipt at block 409. Invarious embodiments, the recorded time and policy information may beused to form a log or record of the activities of the admin user 135,which may be useful if the admin user 135 wishes to recreate a policy orthe like that the admin user 135 had created or used in the past.

At block 417, the system 115 does a check to determine whether afingerprint (e.g., fingerprint 310) of the data source 125 exists. Invarious embodiments, this may be done, for example, by determiningwhether there is a fingerprint file 310 for the data source 125 in thefingerprint cache 221.

In some implementations, the admin user 135 may specify to the system115 which data source(s) 125 to use from among a plurality of datasources which with the system 115 functions; while in otherimplementations, the system 115 may be dedicated to one specific datasource 125.

In some implementations, after determining that a fingerprint 310representing the data source 125 exists, an additional check (not shown)may be executed in conjunction with block 417 to determine whether theexisting fingerprint 310 is recent enough to use. For example, thesystem 115 may determine whether or not the existing fingerprint file310 was created after a predetermined time in the past, such as one dayago, two days ago, five days ago, seven days ago, 14 days ago, 30 daysago, 60 days ago, 90 days ago, one year ago, or the like. Thispredetermined time may be based on how often and/or how much the data ina data source 125 is changed or is updated; e.g., the more often thedata changes, the shorter the predetermined time-in-the past threshold.

If a fingerprint does not exit (or optionally if it is older than thetime-in-the past threshold (e.g., more than 14 days old)), (317 No),then a new fingerprint 310 is generated from the data source 125, forexample, using the process for fingerprint generation as shown in FIG.4B.

If the fingerprint 310 exits (and optionally if it is not older than thetime-in-the past threshold (e.g., not more than 14 days old)) (317,yes), then the process 400 proceeds to block 425.

At block 425, the system 115 determines the information loss using thepolicy 217 that was received at block 405 and the fingerprint 310 of thedata source 125. In some implementations, the information loss producedby the policy 217 can be measured, calculated, or evaluated for a singlecolumn of the data source 125 that is represented by the fingerprint310. While in other implementations, the information loss produced bythe policy 217 can be measured, calculated, or evaluated for multiplecolumns, e.g., on a column by column basis, and the fingerprint 310 mayhave different ridges for different columns of the data source 125. Insome implementations, the system 115 may weight some columns (e.g.,columns with extremely sensitive information, such as SSN) more heavilythan others in quantifying the information loss. A detailed example of aprocess for determining the information loss is shown in FIG. 4C.

In various implementations of block 425, the system 115 calculates ameasurement of the disparity between a dataset (e.g., column of data)with and without the policy 217 applied; or in other words, an estimateof the amount of obscuration of the data that would be induced by theapplication of the policy 217. In various implementations, the system115 can produce this information-loss estimate in the form of a numberon a scale from zero to one. For example, an information-loss estimateof 1.00 means the policy 217 completely obliterated all information inthe dataset; while an information-loss estimate of 0.00 means the policy217 made no change to the original dataset. Similarly, aninformation-loss estimate of 0.05 means the policy 217 had very littleimpact on the dataset, e.g., it obscured very little of the data and/orchanged or hid the data in a minor way; while an information-lossestimate of 0.95 means the policy 217 had a large impact on the data,e.g., it obscured much of the data and/or changed or hid most of thedata.

In various embodiments, the system 115 determines information loss bycomparing the obscured data that is visible or accessible to a queryuser 105/client device 110 after the policy 217 is applied, to theun-obscured raw data and quantifying the difference. This may becalculated, in some implementations, as a reduction in resolution causedby the obscuration policy. As another example, in some implementations,the system 115 may calculate the percentage of information that isredacted or suppressed by the policy 217. For instance, for a dataset(e.g., column) that contains nine digit social security numbers, if apolicy 217 removes or suppresses the first three digits of the dataset(i.e., a query user 105 can see only the last six digits of the socialsecurity numbers), then the system 115 may calculate an information lossvalue of 0.33 (i.e., 3/9) for the policy 217 as applied to this dataset;similarly, if a policy 217 removes or suppresses the first five digitsof the dataset (i.e., a query user 105 can see only the last four digitsof the social security numbers), then the system 115 may calculate aninformation loss value of 0.56 (i.e., 5/9) for the policy 217 and thisdataset. In another example, for a dataset (e.g., column) that containsstate names, if a policy 217 removes or suppresses the rows of the datasource 125 that contain Wyoming as the state name (i.e., a query user105 can see only the rows from states other than Wyoming), then thesystem 115 may count or otherwise measure the number of occurrences of“Wyoming” in the “State Name” column and divide that by the total numberof rows in order to calculate an information loss value. In thisexample, if the number of occurrences of Wyoming is 578 and the totalnumber of rows in the dataset is 32,753, then the system 115 maycalculate an information loss value of 0.02 for the policy 217 ofsuppressing the Wyoming rows in this dataset.

In various implementations, the system 115 can additionally oralternatively calculate and generate other information-loss metrics andinformation besides the above-described information-loss estimate numberon a scale from zero to one. For example, in the case of a roundingpolicy, the system 115 can generate one or more histograms of therounded and/or unrounded dataset and/or various statistical metricsrepresenting the rounded and/or unrounded dataset.

In some of the embodiments described above, the information-lossestimate number represents the information loss for one column of dataafter application of a policy to that column. Additionally oralternatively, the system 115 can calculate or determine aninformation-loss estimate number for, or that takes into account, otherpart(s) of the data source 125 in addition to the column to which thepolicy 217 was applied, where these other part(s) of the data source 125are secondarily affected by the application of the policy. This isparticularly applicable for policies that remove rows of data based onthe values in a specific column(s), because the removed rows will skewor affect the makeup of the data in all, or most of, the other rows tovarious degrees.

For example, consider the case of a policy 217 that suppresses orremoves rows from a data source 125 based on a specific value in aspecific column, such as removing the rows that have the value“Wisconsin” in a “State Name” column. Further consider that the datasource 125 also has another column for “Occupation,” which includescharacter strings for the occupation “dairy farmer.” Because there are alarge number of dairy farmers in Wisconsin compared to most other states(i.e., non-uniformities in the population), removing the “Wisconsin”rows has a significant secondary effect on the content and makeup of the“Occupation” column dataset, causing a disproportionate amount ofinformation loss or disparity in the amount of dairy farmers in theOccupation column; i.e., after the policy is applied, the percentage ofdairy farmers across all occupations is significantly lower than in theraw dataset. Various embodiments consistent with the invention take thisinto account when determining information loss, for example, bycalculating an information-loss estimate for some or all columns if apolicy 127 specifies removal of rows of data.

At block 431, the system 115 reports the calculated, quantifiedinformation loss to the admin user 135 and/or the admin device 140, forexample, in an information-loss report 139.

FIG. 10A shows an example of how information-loss information ispresented to the user for categorical data. In this figure, thecross-hatched “new value” bars show the frequency of a value after adata policy is applied. The dotted “baseline confidence interval”regions show the frequency of a value without any policy. And, the heavyvertical lines in the baseline confidence interval regions show thebaseline value for the attribute (e.g., the data from the “SupplierState” column). In the example of information-loss information shown inFIG. 10A, as shown at the bottom, records from the states of WASHINGTON,NEW MEXICO, TEXAS, and NEW YORK are removed from the dataset, perturbingthe relative frequencies of the remaining items away from their baselinevalues in several instances, although all except DELAWARE are withintheir baseline confidence interval regions. FIG. 10B shows an example ofan information-loss report that was generated for numeric data. In thisexample, a generalization policy is applied to the “Gross Profit” columnon a table, slightly perturbing the descriptive statistics of theunderlying data away from their baseline values. FIG. 10C shows anexample of information-loss information in the form of a summary of thedifferences, over all columns, produced by the applied policy. Theseverity value for each row gives a statistical quantification (e.g., ona scale of 0.000 to 1.000) of how different each column's distributionis from its baseline in the presence of the new policy.

Referring again to FIG. 4A, in some implementations, the admin user 135and/or an application running on the admin device 140 may evaluate thereported information-loss information to determine whether or not thepolicy 217 from block 405 provides sufficient privacy (e.g., a highenough amount of information loss to protect sensitive data) and/orsufficient utility (e.g., a low enough amount of information loss forthe data in the result 119 to be useful for a specific purpose). And, byconsidering the system's objectively calculated information-lossinformation, the admin user 135 can get a qualitative feel for how muchthe data is impacted by a policy and/or by a change from one policy toanother.

In some such implementations, the admin user 135 and/or the admin device140 can, for example, compare the information-loss estimate number(e.g., ranging from 0.00 to 1.00 as described above) to a targetinformation-loss number, plus or minus some tolerance(s), such as +0.05and −0.02. And, if the calculated information-loss estimate number doesnot match the target information-loss number plus or minus thetolerances, then the admin user 135 and/or the admin device 140 mayiteratively provide a new or adjusted policy 217 at block 405 for theprocess 400 to evaluate, until the target information-loss number isreached. Otherwise, when the calculated information-loss estimate numbermatches the target information-loss number plus or minus the tolerances,then the process 400 can proceed to block 435.

At block 435, the system 115 applies the policy 217 to the data source125. In various implementations, this may include storing the policy 217and its associated parameters 219 in the storage system 235, andsubsequently processing each query 117 to determine whether the storedpolicy 217 and its associated parameters 219 are applicable to theparticular query user 105, data source 125, and/or virtualized database123 specified by the query 117. If a received query 217 is one that theprivacy policy 217 covers, then the system 115 applies the obscuringtechniques specified by the policy 217 to the query-responsive databefore the result 119 is provided to the client device 110. Thus, thequery user 105 can only access or see the requested data after the datahas been obscured according to the applicable privacy policy 217.

As noted previously, in some embodiments, the functionality of the admindevice 140 can be implemented by the computing system 115, and asoftware application or the like may take the place of the admin user135, such that the operations 431 and 435 can be automatically donebased on the determined information-loss estimate matching apredetermined target information-loss number, plus or minus atolerance(s). In such embodiments, the system 115 can automaticallytrigger or control the application of a policy that is objectivelyselected to meet a specific information loss requirement, withoutrun-time input from the admin user 135.

FIG. 4B is a block diagram showing an example of a fingerprintgeneration process 450. In some embodiments, all or part of the process450 may be implemented by the computing system 115, for example byexecuting the policy engine 130. As noted with regard to FIG. 3 , afingerprint 310 can be implemented as a set collection of ridges, eachof which may be a file or data structure containing measurements,statistics, artifacts, or the like that are measured or derived from adata source 125, e.g., from a column or other dataset in the data source125.

In various embodiments, the process 450 will generate one or more of theridges 315, 320, 330, 335 for a dataset (e.g., a column) of the datasource 125, depending on the type of data in the dataset. For example,if a column contains numerical data, such as in a column that records“age in years” or “annual income,” then the system 115 will generate anumeric ridge 315 for that dataset. For another example, if the columncontains string data, such as the string-type attributes “yes” or “no”in a column that records the yes/no answer to “U.S. Citizen?” or“Employed?”, then the system 115 will generate a cardinality ridge 315for that dataset.

In some embodiments, the system 115 may interact with the admin user 135to provide a framework that enables the user 135 to develop and/or plugin new metrics/ridges that they have created.

In the example shown in FIG. 4B, the process 450 starts at block 442 bydetermining a sample size, which may be different for different ridges.For example, in the case of descriptive statistic ridges, the system 115may determine the sample size based on or controlled by the minimumsample size required for the sampling error to begin to show asymptoticbehavior. Other standard statistical techniques instead of asymptoticbehavior can also be used to calculate a sample size that is, forexample, statistically significant. In some implementations, the samplesize may be predefined based on the table size or number of rows, anddetermining the sample size at 442 may simply involve looking it up. Forexample, when the table or column has a size 1-1000 (e.g. having 1-1000rows), the sample size=the table size; when the table or column has asize 1001-5000, the sample size=1000; when the table or column has asize 5001-10000, the sample size=2000; etc.

For another example, in the case of sketching approaches, (e.g.count-min sketch), the system 115 may determine the sample size based onlinear table scans of the data source 125.

Once the sample size is determined, at block 445 the system 115 samplesthe data source 125 in accordance with the determined sample size tocreate a representative sample of, e.g., the data in a column of thedata source 125. In various implementations, the system 115 may employrandomized sampling, stratified sampling, hypercube sampling, lineartable scan, or other appropriate sampling regimes.

Using this representative sample, at block 439 the system 115 determinesthe ridge statistics by performing the procedures, algorithms,calculations, and/or operations that produce the contents of a ridge,which contents are different for each of the different ridge types315-335. Ridge statistics are any descriptive statistics that can bemeasured on a random sample of data. These statistics can include, butare not limited to, averages, variances, categorical counts, histograms,covariances, etc.

For example, in the case of a cardinality ridge 315 (see FIG. 6 foradditional details), the system 115: employs a standard statisticalalgorithm to estimate the number of unobserved attributes or values thatare missing from the representative sample; determines the cardinalityof the representative sample by counting the actual number of differentattributes in the sample; employs a standard statistical algorithm toextrapolate the cardinality of the raw dataset (e.g., of the data source125) based on the number of unobserved attributes and the cardinality ofthe representative sample; calculates the number of distinct attributesas a percentage; calculates the percentage of the number of unobservedattributes in the sample size; stores the size of the representativesample; calculates the percentage of the size of the representativesample over the size of the entire dataset; and calculates thepercentage of appearance or occurrence of the most common attributes—forexample the percentage of occurrence of the top 20 most commonattributes.

At block 453, the system 115 stores the ridge statics, for example in afile or data structure for one of the ridge types 315-335, several ofwhich may be associated to make a fingerprint 310. In variousembodiments, the ridge statistics/files may be stored in the fingerprintcache 221. The stored fingerprint 310 (i.e., set of ridges) is used tomeasure and estimate the impact of a privacy policy 217 on theunderlying data source 125, e.g., as described above with respect toblock 425 and elsewhere herein.

FIG. 4C is a block diagram showing an example of a process 460 fordetermining information loss for a policy 217 using the fingerprint 310of a data source 125. This example uses precomputed ranges, which may bestored as part of the fingerprint 310. Thus, in differentimplementations, blocks 463-469 of the process 460 can be performed aspart of a fingerprinting process, such as added on as part of theprocess 450 shown in FIG. 4B, and the results stored in a ridge of thefingerprint 310 for use by the process 460 when needed.

In the example shown, at block 463, the system 115 measures the entropyof the representative sample (see block 445 of FIG. 4B) from the datasource 125, with no policies applied, to get a baseline measurement. Insome embodiments, the entropy can be measured using an informationtheory measurement such as Shannon's entropy. Entropy is closely relatedto information loss, and entropy may be thought of as a measure of theamount of information in a dataset; thus it is analogous to the converseof information loss. That is, a decrease in entropy represents anincrease in information loss.

In measuring the impact of a privacy policy and its obscurationtechnique(s) on a dataset, it is noted that entropy will be maximizedwithout any policies applied to the dataset. Furthermore, as the setx_(Support) becomes more discrete, entropy will decrease monotonically.

At block 465 the process 460 identifies any high-leverage generalizationranges in the representative sample, where a high-leveragegeneralization range is a portion or series of data points where a rapidchange in entropy is identified. One example would be at or above theaverage interstitial distance between an ordered list of observations.These high leverage points or ranges indicate where the entropy curve isbest sampled to reduce the error in interpolating the curve, (forexample to calculate an information-loss value at block 473).

In various implementations, the system 115 can identify thehigh-leverage generalization range(s) by applying a series ofgeneralization values (e.g., rounding values, such as round to thenearest $1000, $2000, $3000, $4000, $5000, etc.) to the representativesample and measuring the entropy throughout the series until the entropynears zero, which will generate a curve. The system 115 can then lookfor inflexion point(s) or an inflexion range(s) on that curve where theentropy changes significantly (e.g., the curve becomes steeper), whichis the high leverage generalization range(s).

Once a high leverage generalization range is identified, at block 467,the system 115 can create a new series of generalization values (i.e.,the high leverage generalization points) that span the high leveragegeneralization range (e.g., in $100 increments to continue the previousexample) and apply them to the representative sample in the highleverage generalization range, and then at block 469, calculate ormeasure the entropy for each of the points to obtain a dense number ofentropy data points in the high leverage range. The group of entropymeasurements can form the basis of a piecewise interpolant (e.g., apiecewise polynomial curve), which is stored by the system 115, (e.g.,as part of a fingerprint 310). Thus, the piecewise interpolant has,rather than uniform sampling throughout, a denser sampling in thehigh-leverage range(s) where the entropy curve is steep, whichsignificantly decreases the error from interpolation using the curve togenerate an entropy estimate, and indirectly, an information-lossestimate.

At block 471, the system 115 receives a generalization range or value(e.g., a value to which to round a column of data), for example from thepolicy 217 that was received at block 405 of FIG. 4A.

At block 473, the system 115 uses the piecewise interpolant from block469 (which may be part of the fingerprint 310) to approximate orestimate the entropy associated with the received generalization rangeor value from the policy 217, and by extension to estimate theinformation loss introduced by the policy 217. For example, if thedataset contains annual salary amounts, and the policy 217 specifiesrounding to the nearest $3,500, the system looks up the piecewiseinterpolant for $3500 and gets or calculates the corresponding entropyestimate.

In various implementations, as noted, the calculated entropy from block473 corresponds to, represents, or is an indirect measurement of theinformation loss. At block 475, the system 115 converts the entropyvalue into an information-loss estimate value.

Similarly, for obscuration types other than generalization, the system115 can analyze the dataset and/or representative sample without andwith the policy's obscuration applied, and the information content canbe measured. The information content can be quantified using aninformation theoretic metric, such as Shannon's Entropy, a signal tonoise ratio, or the like.

Shannon's Entropy is defined as the expectation value of the log of theprobability of some observed outcome:

${H(x)} = {- {\sum\limits_{i}{p_{i}\log p_{i}}}}$

In this expression, p_(i) is the probability of observing the i^(th)value in a dataset. In this expression, H(x) is bounded between 0 andlog(K), where K is the number of distinct values in a dataset. Invarious implementations, information loss can be measured as the changein H(x) introduced by the perturbation on an attribute. For example witha suppress technique or policy 987 (see FIG. 9 ), H(x) would be zero,making the information loss identically H(x) without policies applied.In the case of a generalize technique or policy 383, the values aremapped from a space of K values into a space of K′ possible values,where K′<K. An obfuscate technique or policy 385, will typically, butnot necessarily, maintain counting statistics, keeping H(x) constant andintroducing no information loss.

A randomize technique or policy 389 will either maintain or increase adiversity of values into a dataset, and, in all cases, produce a moreuniform distribution of values, leading to an increase in entropy. Undera Shannon's entropy construction, a randomize technique will create adeceptive increase in information content. In this scenario, variousembodiments of the system 115 can more appropriately representinformation loss as the change in the signal to noise ratio of the data.In general the Signal to Noise Ratio (SNR) is unknown in the data priorto policy application. However obscurations can either reduce signal orincrease noise. As such the change in SNR can be modeled as follows:

${SNR}_{policy} = {{SNR}_{0} \times \left( {1 - \frac{\mathcal{a}}{\beta}} \right)}$

Where a denotes a decrease in signal and β denotes an increase in noise.By convention a ≥1 and β≤1. In this way SNR_(Policy)≤SNR₀, whereSNR_(Policy) is the SNR after the obscuration, and SNR₀ is the raw SNR.In the case of a randomize technique or policy 389, this amounts toquantifying the scale of noise added by the randomization process. Sincerandomization can be seen as convolving the true signal with someobscuring function, various embodiments can estimate the noise as anadditive noise and quantify it using either information content of thenoise or some other information theoretic measure.

One of ordinary skill will recognize that the processes 400, 450, and460 of FIGS. 4A-C are presented for conciseness and clarity ofexplanation, and that blocks and operations may be added to, deletedfrom, reordered, performed in parallel, or modified within process 400without departing from the principles of the invention. For example, inthe process 400, blocks may be added to compare the information-lossestimate to a target information-loss number and either loop back to thetop to try a different policy or automatically apply the policy. Othervariations are possible within the scope of the invention.

FIG. 5 shows an example of the descriptive statistics, attributes,characteristics, calculated values, etc., of a basic numeric ridge 315,which in various embodiments can be generated by the system 115 from adataset (e.g., a column of date from the data source 125) and stored ina file, a data structure, or the like, for example in the fingerprintcache 221.

In the example shown in FIG. 5 , the system 115 has calculated a set ofvalues and saved them in the data structure shown. In this example, IQRis the inner quartile range, which is a measure of statisticaldispersion (e.g., the width of the distribution of the dataset). Q05,Q25, Q75, and Q95 are the fifth, 25^(th), 75^(th), and 95th quantiles ofthe dataset. Mean is the well-known statistical average value of thedataset. Median is the well-known statistical median value of thedataset. Keratosis, skewness and variance are the well-known standarddescriptive statistics for this dataset. Bin counts, bin size, and binlower limits represent the measurements for a histogram for the dataset.Blurred min and blurred max represent the approximate min and max of thedataset, but with some random factor added so as to avoid disclosingactual raw data from the dataset in the fingerprint 210. Sample size thesize of the dataset, here, 10,490 samples or rows. Percent nulls is thenumber of nulls in the dataset, expressed as a percentage of the totaldataset. And, mean absolute deviation is that well-known standarddescriptive statistic for this dataset.

As noted previously, in various embodiments, the system 115 willgenerate a numeric ridge, e.g., as shown in FIG. 5 , only if the datasetcontains numeric data. Thus, if the dataset consisted of characterstrings, for example, last names, then the system 115 will not generatea numeric ridge 315 for that data.

FIG. 6 shows an example of the frequency statistics, attributes, values,etc., of a cardinality ridge 320, which in various embodiments can begenerated by the system 115 from a dataset (e.g., a column of date fromthe data source 125) and stored in a file, a data structure, or thelike, for example in the fingerprint cache 221. In FIG. 6 , the datafrom the cardinality ridge 320 is represented in a tabular format forease of explanation and clarity.

In the example shown in FIG. 6 , the raw dataset contained 10,490samples or rows, and each sample contained a character string having avalue or attribute of either “Y” (for yes) or “N” (for no). The system115 analyzed the entire dataset to generate the fingerprint, and thusthe size of the representative sample is the same as the size of the rawdata set.

In the example shown, the top row 601 contains the number of unobservedattributes or values that are in the raw dataset but not in therepresentative sample used to generate this ridge, (i.e., that areunobserved in the representative sample), as calculated by the system115. In various embodiments, the system 115 may perform standardstatistical analysis to estimate the number of unobserved uniqueattributes, and then use that estimate to extrapolate the truecardinality of the dataset (row 602). In the example shown, because thesample size is equal to the data set size, there are zero unobservedattributes, as shown in the column labelled “Value”.

The second row 602 contains the extrapolated cardinality of the dataset,as calculated by the system 115. In various embodiments, this can becalculated by adding the number of unobserved attributes (row 601) plusthe cardinality of the samples (row 603).

The third row 603 contains the cardinality of the attributes in therepresentative sample (i.e., the number of distinct attributes in thesample), which is counted by the system 115. In this example, there areonly two distinct attributes in the samples: “Y” and “N”, and thereforethe cardinality of the samples is 2. It is also noted that in thisexample, the extrapolated cardinality of the raw dataset is the same asthe actual cardinality of the samples because the system 115 sampled theentire dataset.

The fourth row 604 contains the percentage of distinct attributes.Percent distinct is measured as the ratio between the extrapolatedcardinality (row 602) and the total population. The total population isestimated by the sample size (row 606) divided by the sample fraction(row 607).

The fifth row 605 contains the percentage of null, which is calculatedby the system 115 by dividing the number of unobserved attributes (row601) by the total population.

The sixth row 606 contains the size of the sample taken from the rawdata source 125, which is counted by the system 115.

The seventh row 607 contains the sample fraction, which the system 115calculates by dividing the sample size (row 606) by the size of the datasource from which the sample is drawn. In this example, the sample sizeis equal to the data source size (e.g., all of the data in the datasource was used in the sample), and thus the sample fraction is 1.0 or100%.

The eighth row 608 contains the frequency of occurrence of the mostcommonly occurring attribute in the data set, which the system 115calculates by dividing the number of occurrences by the total samplesize (row 606). In this example, the attribute “N” is the most commonlyoccurring attribute, and it appeared in 99.3232% of the rows in thesample.

The ninth row 609 contains the frequency of occurrence of the secondmost commonly occurring attribute in the data set, which the system 115calculates by dividing the number of occurrences for that attribute bythe total sample size (row 606). In this example, the attribute “Y” isthe second most commonly occurring attribute, and it appeared in 0.6768%of the rows in the sample.

In other examples of cardinality ridge data that have more than twoattribute values, there may be a larger number of most common attributerows similar to the eighth and ninth rows (608, 609) of FIG. 6 . Forexample, the system 115 may determine and calculate the frequency ofoccurrence for the top five, 10, 20, 30, etc. most commonly occurringattributes, or for the number of attributes that together make up 60% ofsample size, or the like. For example, if the dataset contained U.S.state names and the names appeared in the sample approximately inproportion to each state's population, then the four most commonattribute rows starting at 608 might be California 11.9%, Texas 8.0%,Florida 6.8%, and New York 6.2%.

As noted previously, in various embodiments, the system 115 willgenerate a cardinality ridge 320, e.g., as shown in FIG. 6 , only if thedataset contains a finite, repeating set of attributes, such as gender,occupation, city name, state name, and the like. If the dataset containsnumeric attributes or a set of unique, non-repeating attributes, whetherstring or numeric, such as social security numbers or bank accountnumbers, then the system 115 will not generate a cardinality ridge 320for that data.

FIG. 7 shows an example of the frequency statistics, attributes, values,etc., of a sensitivity ridge 335, which in various embodiments can begenerated by the system 115 from a data source 125 and stored in a file,a data structure, or the like, for example in the fingerprint cache 221.

In various implementations, to generate the sensitivity ridge 335, thesystem 115 can, for example, assess, analyze, or calculate the contentsof the data source 125 against predetermined descriptors thatcharacterize various sensitive data types, including but not limited toSOCIAL SECURITY NUMBER, CREDIT CARD NUMBER, PASSPORT NUMBER, GENDER, andADDRESS. Sensitive data types can be modeled using a combination of textpatterns (for example the pattern for social security number would be 9digits with hyphens between the third and fourth digit and fifth andsixth digits), checksums (for example credit card numbers), and list ofknown values (for example United States ZIP codes or genders). Thesepatterns, dictionaries, and checksums are used to detect the presence ofpotentially sensitive data within a data source. FIG. 7 shows an exampleof the reported results for a data source. Each attribute (e.g., column)within a data source will have an entry in the sensitivity ridge 335,with each entry being a list of sensitive data types (if any) that matchthe pattern(s) in the data. In this example the “website,” “gender,”“passport,” and “date_time_of_purchase” attributes are consistent withthe sensitive data types “URL,” “GENDER,” “FRANCE_PASSPORT,” and “DATE”and “TIME,” respectively; while “purchase_amount” and “purchase_number”do not match any sensitive data types. The admin user 135 or anapplication running on the admin device 140 can use the information inthe sensitivity ridge 335 to identify which attributes in a data source125 are most sensitive and, for example, apply more restrictive policies(e.g., policies that cause more information loss) to their datasets, forexample, based on a set of rules.

FIGS. 8A and 8B together show an example of the frequency statistics,attributes, values, etc., of a string ridge 330, which in variousembodiments can be generated by the system 115 from a data source 125(e.g., from the columns in a data source 125, where each column has itsown entry or data structure) and stored in a file, a data structure, orthe like, for example in the fingerprint cache 221.

In various implementations, to generate the string ridge 330, the system115 can, for example, assess, analyze, or calculate the format andcharacteristics of strings attributes (e.g., columns) within thedataset. Similar to the cardinality ridge 320, this string ridge 330contains the number of missing elements seen in each string attribute,expressed as a percentage, using the field “Percent NULL.” In theexample shown, the fields: Average String Length, Maximum String Length,and Minimum String Length, represent the average, maximum, and minimumnumber of characters in each string, respectively. Average White Space,Average Upper Case Characters, and Average Lower Case Charactersrepresent the average number of character in each string that arespaces, upper case ([A-Z]), or lower case ([a-z]), respectively.

Each string is further decomposed into a regular expression. This isdone by breaking each string down into a series of contiguous charactertypes: upper case ([A-Z]), lower case ([a-z]), digits ([\d]), whitespace ([\s]), and everything character type ([{circumflex over( )}A-Za-zMdMs]). This decomposition is assembled into a regularexpression that matches the observed string. The frequency of eachunique regular expression is counted.

The field Leading Regular Expressions represents the most frequentlyoccurring distinct regular expression. The field Leading RegularExpression Frequencies is the number of times each leading regularexpression occurs. In various embodiments, the system 115 may use theresults of the string ridge 330 to discover consistent patterns in thetext, which may be used to augment the patterns within the sensitivityridge 335 and discover unforeseen sensitive attributes, for example,provider-specific attributes such as medical plan numbers or medicalrecord numbers.

FIG. 9 shows an example of several obscurations, which may be, or beincluded in, a policy 217. The obscurations shown in this non-limitingexample include five different processes, algorithms, or techniques thatcan be performed on a dataset: generalize 983, obfuscate 985, suppress987, randomize 989, and redact 991. In various embodiments of the system100, an admin user 135 can create, select, and/or modify a policy 217 toinclude one or more of the obscuration techniques 983-991. As shown inFIG. 9 , the system 115 may apply one or more of the obscurationtechniques 983-991 to the raw data 981, e.g., the data in the datasource 125 and/or the virtualized database 123, and produce obscureddata 993. The obscured data 993 may be provided to a query user 105 inresponse to a query 117, and/or the obscured data 993 may be used by thesystem 115 to calculate the amount of information loss caused by apolicy 217 that includes one or more of the obscuration techniques983-991.

In various implementations, generalize 983 can be a process whichreduces the precision of any datum. The implementations can take severalforms, including but not limited to rounding off numeric attributes toarbitrary precision, bucketing numeric values into predefined buckets,bucketing date and/or time data to predefined buckets, or generalizingcategorical data into less discriminating value. An example of roundingwould be rounding a dollar value such as $37,450.45 to the nearestthousand ($37,000.00). An example of bucketing may be converting agevalues into predefined buckets for the age brackets of 00-14, 14-18,18-65, and 65 and over. In this example scheme, an individual of age 35would be simply bucketed into the 18-65 bucket, providing increasedanonymity on their true age. Bucketing date or time data could take theform of representing the date, Apr. 1, 2019 as simply a month-yearbucket (April 2019), a year bucket (2019), or some other defined date ortime precision. Generalizing categorical attributes can take the form ofrolling up some category into a category which is a superset of theexisting value. An example would be representing the city, Ottumwa, Iowaas either the county (Wapello County, Iowa), the state (Iowa), or thecountry (United States).

In various implementations, obfuscate 985 can be a process for replacingattributes from a data source 125 with some obscured value. Theimplementations could involve tokenization, hashing, encrypting, orotherwise replacing the sensitive data. For example the value orattribute “Emma Smith” could be represented using a unique hash of thestring, such as “1c272047233576d77a9b9a1acfdf741c.” This obscures theoriginal value (Emma Smith), while retaining a 1:1 mapping with theoriginal value. As a result the obscured data still retains informationcontent. Other implementations of obfuscation mechanisms includeobscuring the surname, and exposing only “Emma,” tokenizing using areversible process with a code book or dictionary, and encrypting thedata.

In various implementations, suppress 987 can include removing orreplacing the value of an attribute from the data. For example,replacing all names with a placeholder such as “Jane Doe” or an emptystring. This process severely reduces the information content of anattribute in a dataset 125.

In various implementations, randomize 989 can replace an attribute atrandom according to some non-zero probability. This type of obscuringtechnique will provide plausible uncertainty regarding the value of theattribute in any single record, while preserving some of the informationcontent of the underlying data. Randomization mechanisms can include arandomized response, local differential privacy, or other stochasticperturbative process.

In various implementations, redact 991 can be the conditional removal ofa record or set of records from the dataset. This assures that certainrecords are not included in specific analyses or query results, inaccordance with the right to be forgotten, residency requirements, orusage restrictions.

As noted previously, each of the obscuration techniques 983 through 991can be applied, e.g., via a policy 217, either independently or inconjunction to create the obscured dataset 993.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

What is claimed is:
 1. A computer-implemented method for measuring animpact of a data privacy policy, the method comprising: sampling a datasource to obtain a sample of data that is statistically representative;determining ridge statistics for the sample of data; measuring a firstentropy of the sample of data; applying the data privacy policy to thesample of data; measuring a second entropy of the sample of data withthe policy applied; calculating an information loss value based on thedifference between the first entropy and the second entropy; andpresenting the information loss value.
 2. The method of claim 1, furthercomprising: applying the data privacy policy to the data source based onthe information loss value.
 3. A computer-implemented method formeasuring information loss, the method comprising: sampling a datasource to obtain a sample of data that is statistically representative;determining ridge statistics for the sample of data; receiving a dataprivacy policy for a dataset of the data source; determining an estimateof information loss caused by the data privacy policy using the ridgestatistics; and presenting the estimate of the information loss.
 4. Themethod of claim 3, further comprising: applying the data privacy policyto the data source based on the estimate of the information loss.
 5. Themethod of claim 3, wherein determining ridge statistics for the sampleof data comprises creating numeric ridge statistics for the sample ofdata.
 6. The method of claim 3, wherein determining ridge statistics forthe sample of data comprises creating cardinality ridge statistics forthe sample of data.
 7. The method of claim 3, wherein determining ridgestatistics for the sample of data comprises creating string ridgestatistics for the sample of data.
 8. The method of claim 3, whereindetermining ridge statistics for the sample of data comprises creatingsensitivity ridge statistics for the sample of data.
 9. A system formeasuring information loss for a data source, the system comprising: acomputer-readable data storage device containing program instructions;and a processor, operably connected to the computer-readable datastorage device, that executes the program instructions to performoperations comprising: determining one or more ridge statistics for thedata source; receiving a data privacy policy for the data source;determining an estimate of information loss caused by the data privacypolicy using the one or more ridge statistics; and presenting theestimate of the information loss.
 10. The system of claim 9, wherein theoperations further comprise sampling the data source to obtain a sampleof data that is statistically representative.
 11. The system of claim10, wherein determining one or more ridge statistics for the data sourcecomprises determining one or more ridge statistics for the sample ofdata.
 12. The system of claim 9, wherein the operations further compriseapplying the data privacy policy to the data source.
 13. The system ofclaim 9, wherein determining one or more ridge statistics for the datasource comprises at least one of: creating numeric ridge statistics forthe data source, creating cardinality ridge statistics for the datasource, creating string ridge statistics for the data source, orcreating sensitivity ridge statistics for the data source.
 14. Thesystem of claim 9, wherein determining one or more ridge statistics forthe data source comprises obtaining one or more ridge statistics thatwere previously stored.
 15. A computer-implemented method measuringinformation loss for a data source, the method comprising: determiningone or more ridge statistics for the data source; receiving a dataprivacy policy for the data source; determining an estimate ofinformation loss caused by the data privacy policy using the one or moreridge statistics; and presenting the estimate of the information loss.16. The method of claim 15, further comprising sampling the data sourceto obtain a sample of data that is statistically representative.
 17. Themethod of claim 16, wherein determining one or more ridge statistics forthe data source comprises determining one or more ridge statistics forthe sample of data.
 18. The method of claim 15, further comprisingapplying the data privacy policy to the data source.
 19. The method ofclaim 15, wherein determining one or more ridge statistics for the datasource comprises at least one of: creating numeric ridge statistics forthe data source, creating cardinality ridge statistics for the datasource, creating string ridge statistics for the data source, orcreating sensitivity ridge statistics for the data source.
 20. Themethod of claim 15, wherein determining one or more ridge statistics forthe data source comprises obtaining one or more ridge statistics thatwere previously stored.